Polyurethane-forming compositions are widely used in a variety of commercial, industrial and household applications, such as in automotive clear-coat and seat cushion applications. Polyurethane systems that employ isocyanates which are pre-reacted with monofunctional reagents to form relatively thermally labile compounds are called blocked isocyanates. Uretdiones are a type of blocked isocyanate. Uretdiones are typically prepared by dimerizing an isocyanate to form a uretdione with unreacted isocyanate groups which can then be extended with a polyol to form a polymeric material containing two or more uretdione groups in the polymer chain. In some literature, uretdiones are referred to as “1,3-diaza-2,4-cyclobutanones”, “1,3-diazatidin-2,4-diones”, “2,4-dioxo-1,3-diazetidines”, “urethdiones” or “uretidiones”. Typically, the polymer has few, if any, free isocyanate groups, which is achieved by controlling the stoichiometry of the polyisocyanate, polyol and by the use of a blocking agent.
Polyuretdiones and polyols may react in a very fast fashion in the presence of a tertiary amine catalyst and thus have a short pot-life. To the best of the present inventors' knowledge, no one has developed a cross-linking approach using acid-blocked tertiary amine catalysts in combination with uretdiones and polyols.
To reduce or eliminate pot-life problems, a need exists in the art for an alternative cross-linking approach to obtain compositions having physical properties similar to polyurethane compositions.